Astron. Astrophys. Suppl. Ser. 138, 345-353
The science potential of ALFA: Adaptive optics with natural and laser guide stars
R.I. Davies1 - W. Hackenberg1 - T. Ott1 - A. Eckart1 - S. Rabien1 - S. Anders1 - S. Hippler2 - M. Kasper2 - P. Kalas2 - A. Quirrenbach3 - A. Glindemann4
Send offprint request: R. Davies: firstname.lastname@example.org
1 - Max-Planck-Institut für extraterrestrische Physik, Postfach 1603, D-85740 Garching, Germany
2 - Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany
3 - University of California, San Diego, Physics Dept., Center for Astrophysics & Space Sciences, Mail Code 0424, La Jolla, CA92093-0424, U.S.A.
4 - European Southern Observatory, Karl Schwarzschildstraße 2, D-85748, Garching, Germany
Received February 12; accepted May 25, 1999
Adaptive optics with laser guide stars is mandatory in order to make
use of the full capabilities of 8-m class telescopes.
However, progress has been slow in two particular areas: techniques for
spectroscopy at diffraction limited resolution and wavefront sensing
on laser guide stars.
ALFA - currently the only European laser guide star adaptive optics
system, and the only one in the world open to guest observers - has made
significant advances in both of these.
In this paper we report on our first results from summer 1998,
representing significant improvements over previous performance.
We report on observations using natural guide stars which
demonstrate that for bright stars () ALFA can now reach
K-band Strehl ratios in excess of 60% and easily resolve binaries
at the diffraction limit of the telescope.
We then present some of the first
integral field spectroscopy at diffraction limited scales,
showing we are able to distinguish spectra of binary stars with
a separation of only 0.26.We also discuss results from a wide field image, which indicate that useful
correction (allowing binary stars and circumstellar dust shells to
be resolved) can be achieved from a relatively faint star to a radius of at
least 1.Our last set of results include a
correction on a galaxy using the laser guide star as the reference.
The best result to date is of the galaxy UGC1347 in Abell262.
Correcting tip-tilt on a star 41 away and higher orders on the
laser, we achieved an increase in peak
intensity of 2.5, and a reduction in FWHM from 1.07 to
Key words: instrumentation: adaptive optics -- instrumentation: laser
guide stars -- stars: binaries: close -- stars: pre-main-sequence --
galaxies: individual (UGC 1347)
Copyright The European Southern Observatory (ESO)